For example, in Japanese Laid-Open Patent Publication No. 6-218337, an ultrasonic washer 520 as shown in FIG. 37 is proposed for washing an object to be washed or a portion to be washed by spraying washing from a nozzle, to which vibration energy due to ultrasonic wave is applied.
The conventional ultrasonic washer 520 is comprised of a driving circuit 521, an ultrasonic transducer 522 driven by the driving circuit 521, an ultrasonic wave propagation member 523 for propagating ultrasonic vibration generated by the ultrasonic transducer 522, a cone 524 connected to the ultrasonic wave propagation member 523, a nozzle 525 connected to the cone 524 and serving as a horn to which ultrasonic wave is transmitted through the ultrasonic wave propagation member 523 and the cone 524, a water supply pipe 526 for supplying washing to an inside the nozzle 525, and so on. Since a plurality of flow passages is formed in the inside of the nozzle toward an opening at an end thereof, the ultrasonic vibration propagated to the nozzle 525 is further propagated to the washing while the washing passes through the flow passages. Then, the washing to which the ultrasonic vibration is propagated is sprayed from the opening at the end of the nozzle 525. Since the ultrasonic washer 520 is non-contact type, it is possible to wash a portion to be washed where a surface irregularity is larger.
In the conventional ultrasonic washer 520, the ultrasonic vibration generated by the ultrasonic transducer 525, however, is propagated to the nozzle 525 through the ultrasonic wave propagation member 523 and the cone 524, and further propagated to the washing from side walls of the flow passages of the nozzle 525 while the washing passes through the flow passages of the nozzle 525. Therefore, since transmission efficiency of the ultrasonic vibration is lower, when output power of the ultrasonic transducer 525 is smaller, there is a possibility that enough quantity of bubble is not generated the washing sprayed from the nozzle 525, and enough detergency due to cavitation effect is not provided. On the other hand, when the output power of the ultrasonic transducer 522 is made too high, there is a possibility that the washing becomes mist like a supersonic humidifier, and enough detergency is not provided.
Furthermore, the conventional ultrasonic washer 520 is a large-scale ultrasonic washer for washing, for example, a side wall of establishment, as described in the Publication gazette, in which the driving circuit 521 is independently provided from a main body, so that it has a configuration not suitable to be used on hand by a user.